Gold Electrode Surface Research Articles

A TiO2-adenine nanocomposite as modification material for screen-printed gold electrode to detect H1N1 (swine flu) virus: A disposable genosensor

A genosensor based on TiO2-adenine nanocomposites (NCs) modified screen-printed gold electrode surface (TA-SPGE) was immobilized with haemagglutinin (HA) gene specific probe containing 5′ amine group and investigated for swine flu virus (H1N1). Bare SPGE surface was modified by drop coating of the nanocomposites. The NCs and precursors were characterized structurally and morphologically by adopting various techniques such as Fourier Transform Infrared (FTIR) spectra, X-ray Diffraction (XRD) spectra, UV–Visible spectra, Raman spectra, Zeta sizer, Field-Emission Scanning Electron Microscopy (FE-SEM), Energy Dispersive spectra (EDS) and High-Resolution Transmission Electron Microscopy (HR-TEM) with Selected Area Electron Diffraction (SAED) pattern. Electrochemical techniques termed as cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectra (EIS) were employed for analytical detection of single-stranded viral genome in phosphate buffer saline (pH-7.2) by using methylene blue (MB) redox indicator. Moreover, the performance of designed electrode was optimized at different concentration, pH, and scan rates. The proposed genosensor revealed high sensitivity 10.6 μA/ng.cm2, lower detection limit (LOD) of 6.7 × 10-8 ng/mL and wide linear range of 3 × 10-8-3 × 10-3 ng/mL with regression coefficient of R2 = 0.989 towards swine flu virus DNA. Additionally, the modified genosensor revealed good stability and specificity against human DNA and various pathogens such as H3N2 influenza virus, Bacillus subtilis, Neisseria meningitidis, Staphylococcus aureus and Streptococcus pyogenes. The proposed genosensor is based on relatively simple methodology, quite amicable and could promptly be used as point-of-care test for swine flu virus detection.

Signal amplification of a quartz crystal microbalance immunosensor by gold nanoparticles-polyethyleneimine for hepatitis B biomarker detection

The procedures currently used for hepatitis B (HB) detection are not suitable for screening, clinical diagnosis, and point-of-care testing (POCT). Therefore, we developed and tested a QCM-based immunosensor by surface modification with AuNP-PEIs to amplify the signal and provide an oriented-immobilization surface. The AuNP-PEIs were characterized by ICP-Mass, UV/Vis, DLS, FE-SEM, and ATR-FTIR. After coating AuNP-PEIs on the gold electrode surface, anti-HBsAg antibodies were immobilized using NHS/EDC chemistry based on response surface methodology (RSM) optimization. The efficiency of the immunosensor was assessed by human sera and data were compared to gold-standard ELISA using receiver-operating-characteristic (ROC) analysis. FE-SEM, AFM, EDS, and EDS mapping confirmed AuNP-PEIs are homogeneously distributed on the surface with a high density and purity. After antibody immobilization, the immunosensor exhibited good recognition of HBsAg with a calibration curve of ∆F = − 6.910e-7x + 10(R2 = 0.9905), a LOD of 1.49 ng/mL, and a LOQ of 4.52 ng/mL. The immunosensor yielded reliable and accurate results with a specificity of 100% (95% CI 47.8–100.0) and sensitivity of 100% (95% CI 96.2–100.0). In conclusion, the fabricated immunosensor has the potential as an analytic tool with high sensitivity and specificity. However, further investigations are needed to convert it to a tiny lab-on-chip for HB diagnosis in clinical samples.

The optimization of self-assembled monolayer of thiols on screen-printed gold electrode

<span>The activated gold-modified electrode surface for self-assembled monolayer (SAM) is suitable for N-(3-dimethylaminopropyl)-N-ethylcarbodiimide hydrochloride (EDC), 16-mercaptohexadecanoic acid (16-MDA), and N-hydroxysuccinimide (NHS). The various substrates could potentially be used for surface functionalization that binds to one another. Using modified screen-printed gold electrodes, 16-MDA, EDC, and NHS, we developed a self-assembling monolayer. Different 16-MDA concentrations were applied to the surface of a screen-printed electrode surface to enhance the sensitivity of the working electrode. The impact of different EDC, NHS, and 16-MDA concentrations (0.4 M, 0.8 M, 1 M, 1.2 M, 1.4 M, and 1.8 M) and incubation times between 5 and 30 minutes were examined and compared. The binding surface of the screen-printed gold electrode was characterized using the differential pulse voltammetry (DPV) technique. It has been demonstrated that the substrate concentrations at 5 minutes and 30 minutes of incubation time used to have the highest surface coverage and electron transfer rates. This concentration would be utilized in the subsequent experiment to evaluate the binding of various bacterial species. These findings suggest that the SAM in a modified screen-printed gold electrode may be functionalized to detect microorganisms.</span>

Electron Spin‐Dependent Electrocatalysis for the Oxygen Reduction Reaction in a Chiro‐Self‐Assembled Iron Phthalocyanine Device

AbstractThe chiral‐induced spin selectivity effect (CISS) is a breakthrough phenomenon that has revolutionized the field of electrocatalysis. We report the first study on the electron spin‐dependent electrocatalysis for the oxygen reduction reaction, ORR, using iron phthalocyanine, FePc, a well‐known molecular catalyst for this reaction. The FePc complex belongs to the non‐precious catalysts group, whose active site, FeN4, emulates catalytic centers of biocatalysts such as Cytochrome c. This study presents an experimental platform involving FePc self‐assembled to a gold electrode surface using chiral peptides (L and D enantiomers), i.e., chiro‐self‐assembled FePc systems (CSAFePc). The chiral peptides behave as spin filters axial ligands of the FePc. One of the main findings is that the peptides′ handedness and length in CSAFePc can optimize the kinetics and thermodynamic factors governing ORR. Moreover, the D‐enantiomer promotes the highest electrocatalytic activity of FePc for ORR, shifting the onset potential up to 1.01 V vs. RHE in an alkaline medium, a potential close to the reversible potential of the O2/H2O couple. Therefore, this work has exciting implications for developing highly efficient and bioinspired catalysts, considering that, in biological organisms, biocatalysts that promote O2 reduction to water comprise L‐enantiomers.

Electron Spin-Dependent Electrocatalysis for the Oxygen Reduction Reaction in a Chiro-Self-Assembled Iron Phthalocyanine Device.

The chiral-induced spin selectivity effect (CISS) is a breakthrough phenomenon that has revolutionized the field of electrocatalysis. We report the first study on the electron spin-dependent electrocatalysis for the oxygen reduction reaction, ORR, using iron phthalocyanine, FePc, a well-known molecular catalyst for this reaction. The FePc complex belongs to the non-precious catalysts group, whose active site, FeN4, emulates catalytic centers of biocatalysts such as Cytochrome c. This study presents an experimental platform involving FePc self-assembled to a gold electrode surface using chiral peptides (L and D enantiomers), i.e., chiro-self-assembled FePc systems (CSAFePc). The chiral peptides behave as spin filters axial ligands of the FePc. One of the main findings is that the peptides' handedness and length in CSAFePc can optimize the kinetics and thermodynamic factors governing ORR. Moreover, the D-enantiomer promotes the highest electrocatalytic activity of FePc for ORR, shifting the onset potential up to 1.01 V vs. RHE in an alkaline medium, a potential close to the reversible potential of the O2 /H2 O couple. Therefore, this work has exciting implications for developing highly efficient and bioinspired catalysts, considering that, in biological organisms, biocatalysts that promote O2 reduction to water comprise L-enantiomers.

Cell adhesion molecule immobilized gold surfaces for enhanced neuron-electrode interfaces.

To provide a long-term solution for increasing the biocompatibility of neuroprosthetics, approaches to reduce the side effects of invasive neuro-implantable devices are still in need of improvement. Physical, chemical, and bioactive design aspects of the biomaterials are proven to be important for providing proper cell-to-cell, cell-to-material interactions. Particularly, modification of implant surfaces with bioactive cues, especially cell adhesion molecules (CAMs) that capitalize on native neural adhesion mechanisms, are promising candidates in favor of providing efficient interfaces. Within this concept, this study utilized specific CAMs, namely N-Cadherin (Neural cadherin, N-Cad) and neural cell adhesion molecule (NCAM), to enhance neuron-electrode contact by mimicking the cell-to-ECM interactions for improving the survival of cells and promoting neurite outgrowth. For this purpose, representative gold electrode surfaces were modified with N-Cadherin, NCAM, and the mixture (1:1) of these molecules. Modifications were characterized, and the effect of surface modification on both differentiated and undifferentiated neuroblastoma SH-SY5Y cell lines were compared. The findings demonstrated the successful modification of these molecules which subsequently exhibited biocompatible properties as evidenced by the cell viability results. In cell culture experiments, the CAMs displayed promising results in promoting neurite outgrowth compared to conventional poly-l-lysine coated surfaces, especially NCAM and N-Cad/NCAM modified surfaces clearly showed significant improvement. Overall, this optimized approach is expected to provide an insight into the action mechanisms of cells against the local environment and advance processes for the fabrication of alternative neural interfaces.

Modified Impedance Sensing System Determination of Virulence Characteristics of Pathogenic Bacteria Klebsiella Species.

An impedance sensing system is a family of biosensors that measure changes in electrical impedance to perform their functions. Physical and chemical changes in the impedance of the sensing element, such as changes in the concentration of a target analyte or changes in the physical properties of the sensing element, can result in changes in the impedance of the sensing element. Many impedance biosensors have been developed for the detection of pathogens in the past few decades. Several types of biosensors have been developed for the detection of infections, including transduction elements, biorecognition components, and electrochemical approaches. In this review, we discuss the characteristics and pathogenic factors associated with 2,3-butanediol-producing Klebsiella pneumoniae collected using impedance sensors. An impedance sensing system was introduced as a great method for monitoring the virulence factors of Klebsiella spp. in situ. Klebsiella pneumoniae produces virulence factors, including capsules, lipopolysaccharides, fimbriae, and siderophores, as part of its pathogenesis. It is possible to examine virulence factors' pathogenic characteristics in vitro and in vivo using real tissues or mouse models in order to conduct experiments. For the monitoring of virulence factors in situ, a novel alternative method has been developed to mimic the environment of real tissues. For the purpose of developing tissue-mimicking models, mucin and mannose were used to modify the surface of gold electrodes. These components are known to contribute to the adhesion of pathogens to epithelial cells in mammals.

Synthesis, characterization and computational study of the conjugated thiol-systems for self-assembled monolayers on gold electrode

In the present work, we examine the synthesis and characterization of the Π-conjugated organic molecules applied to immobilize the laccase enzyme on gold electrode surfaces. The density functional theory (DFT) and time-dependent (TD-DFT) were performed to compute the optoelectronic properties. The interactions between the ligand (conjugated thiol system) and the receptor (laccase enzyme) were investigated using docking simulations. The Π-conjugated systems were prepared by the Horner-Wadsworth-Emmons reaction. These conjugated organic molecules were further used to design a new generation of nanostructured bioelectrodes that allow the electrical connection of a laccase enzyme with the gold metallic surface. Direct electron transfer (DET) between the enzyme (laccase) and the gold electrode was achieved in a potentially straightforward manner. This modified cathode could be implemented in new biosensors to assess the concentration of particular analytes, such as the effective detection of O2 for healthcare monitoring and disease diagnosis. It could also be employed to develop promising biofuel cells.

Innovative and efficient electroanalytical approach for determining persulfate in aqueous solutions using a gold electrode

Persulfate (PDS), peroxodisulfate, peroxydisulfate, peroxodisulfuric acid, is an oxidant that can be generated by direct oxidation of sulfate ions or indirectly via reaction with hydroxyl radicals in anodes with high oxygen overpotential. Quantitative methods for determining/quantifying PDS in the presence of other strong oxidants or other anions in eco-friendly applications do not give reliable results because of these interferents. Therefore, an additional method is needed to improve the efficacy to determine/quantify the PDS concentration in oxidative environments. In this frame, an alternative sensing approach was developed based on the electroreduction of PDS in the polycrystalline gold electrode using the square wave voltammetry (SWV) technique for its detection and quantification. Then, the procedure was evaluated in terms of its effectiveness for determining PDS in complex matrices, such as in the electrolysis of sulfate ion precursor solutions using anodes with high oxygen overpotential (e.g.: diamond electrode) capable of generating other strong oxidants. Based on the results obtained, it was confirmed that only the direct electron transfer step is attained when PDS is electrochemically synthetized at the surface of the polycrystalline gold electrode, contributing to its detection and quantification by SWV. It was also observed that at acidic conditions, the PDS electroreduction process is controlled by mass transfer while that the sensitivity for PDS detection is improved, achieving detection limits of about 14 and 19 μM for perchloric and sulfuric acids medium, respectively. When the electrolysis of sulfate-based solution at acidic conditions was performed to determine the electrochemical production of PDS by SWV approach with Au sensor, the concentration of PDS was effectively determined and no interferences were assessed by other strong oxidants generated during the electrolysis. Conversely, the spectrophotometric method showed that, the results of the PDS concentration were overestimated and other strong oxidants significantly interfere with its determination during the electrolysis of sulfuric acid solutions. Therefore, the electroanalytical method presented here is a suitable alternative for determining PDS during the applicability of the environmental-electrochemical technologies.

Highly specific and sensitive sandwich-type electrochemiluminescence biosensor for HPV16 DNA detection based on the base-stacking effect and bovine serum albumin carrier platform

The detection of specific DNA sequences and the identification of single nucleotide polymorphisms are important for disease diagnosis. Herein, by combining the high specificity of the base-stacking effect with the high reproducibility of bovine serum albumin (BSA) modified electrodes and the high loading performance of DNA nanoclews (DNA NCs), a novel sandwich-type electrochemiluminescence (ECL) biosensor is reported for the highly specific detection of HPV16 (chosen as the model target). The capture probes are loaded by BSA carrier platforms modified on the gold electrode surface to improve reproducibility. DNA NCs loaded with a large amount of Ru(phen)32+ worked as signal probes. The template probe is composed of the complementary strand of the target and two free nucleic acid anchors at the head and tail. In the presence of the target DNA, the template probes can form stacked base pairs with target, generating high base-stacking energy. This results in the shorter free anchors of template probes being able to bind to the capture and signal probes. This eventually forms a sandwich structure that allows Ru(phen)32+ to be near the electrode surface, producing an ECL signal. There is a linear relationship between the signal and the target concentration range from 10 fM to 100 pM, with a detection limit of 5.03 fM (S/N=3). Moreover, the base-stacking effect has single base recognition ability for base pairs, effectively avoiding false positive signals. The results of this strategy for clinical samples are consistent with classical methods.

Selective electrochemical determination of dopamine using Thioglycolic acid modified gold electrode

This study was aimed to investigate the selective electrochemical determination for dopamine based on thioglyolic acid-modified gold electrode. Negatively charged Au electrode surface was created by making Thioglycolic acid film through thiol functional group. Greater oxidation current and less overpotential was observed for the oxidation of dopamine in phosphate buffer solution of pH 8.0 at thioglyolic acid-modified gold electrode than bare Au electrode due to the electrostatic attraction between the negatively charged thioglyolic acid-modified gold electrode surface and positively charged dopamine. The electrochemical behavior of dopamine at the thioglyolic acid-modified gold electrode showed a linear response from 0.05 to 100.0 µM and the limit of detection is 0.01 µM using chronoamperommetry. The proposed thioglyolic acid-modified gold electrode shows good repeatability and promising application in dopamine hydrochloride injection sample.

An electrochemical biosensor for T4 polynucleotide kinase activity identification according to host-guest recognition among phosphate pillar[5]arene@palladium nanoparticles@reduced graphene oxide nanocomposite and toluidine blue.

T4 polynucleotide kinase (T4 PNK) helps with DNA recombination and repair. In this work, a phosphate pillar[5]arene@palladium nanoparticles@reduced graphene oxide nanocomposite (PP5@PdNPs@rGO)-based electrochemical biosensor was created to identify T4 PNK activities. The PP5 used to complex toluidine blue (TB) guest molecules is water-soluble. With T4 PNK and ATP, the substrate DNA, which included a 5'-hydroxyl group, initially self-assembled over the gold electrode surface by chemical adsorption of the thiol units. Strong phosphate-Zr4+-phosphate chemistry allowed Zr4+ to act as a bridge between phosphorylated DNA and PP5@PdNPs@rGO. Through a supramolecular host-guest recognition connection, TB molecules were able to penetrate the PP5 cavity, where they produced a stronger electrochemical response. With a 5 × 10-7 U mL-1 detection limit, the electrochemical signal is linear in the 10-6 to 1 U mL-1 T4 PNK concentration range. It was also effective in measuring HeLa cell lysate-related PNK activities and screening PNK inhibitors. Nucleotide kinase-target drug development, clinical diagnostics, and screening for inhibitors all stand to benefit greatly from the suggested technology, which offers a unique sensing mechanism for kinase activity measurement.

O-Fenilendiamin ve Benzokinon Bazlı Polimer Filmle Oluşturulan Kolesterol Biyosensörünün Elektrokimyasal Karakterizasyonu

Aim: The detection of cholesterol concentration in the blood is an important parameter in the diagnosis and follow-up of many diseases, including cardiovascular and hepatobiliary diseases. Nowadays, various methods have been used for the routine analysis of cholesterol, including spectrophotometric, high-performance liquid chromatography (HPLC), and amperometric methods. Since biosensors have advantages such as high sensitivity, fast response, low cost, small size, continuous online detection, and reproducible results, it is aimed to develop a biosensor method for cholesterol determination. Methods: Polymer film immobilization was performed on the gold electrode surface electrochemically in an acetonitrile-water medium containing o-phenylenediamine and benzoquinone. Cholesterol oxidase (ChOx, E.C. 1.1.3.6) enzyme was immobilized on the polymer film-immobilized electrode surface by the self-forming monolayer method. Optimization and characterization studies were carried out for the determination of cholesterol with the prepared electrodes. Results: The determination of cholesterol was performed via monitoring the oxidation current of enzymatically produced H2O2 at 0.70 V Ag/AgCl. Optimum biosensor conditions were determined for phosphate buffer at 0.1M, pH 7.0, and 30°C for the Au/oPD-BQ/ChOx enzyme electrode. The linear working range is 9.8×10-6-1.1×10-2 mM, and the cholesterol detection limit is 9.8×10-6 mM. The analysis of total cholesterol in solutions was performed using the proposed Au/oPD-BQ/ChOx electrode. Conclusion: A convenient, simple, reproducible, and stable method was developed for the determination of cholesterol by immobilizing cholesterol oxidase on the prepared electrode surface through a polymer film. The sensor we designed can be expanded to improve the detection of many analytes in the clinic.

Aptamer-Based Electric-Double -Layer (EDL) Extended-Gated FET Biosensor for Detection of Cadmium Ion

Cadmium ion (Cd2+) is a highly toxic heavy metal pollutant. It causes irreversible damage to human health even at low doses due to a long biological half-life and strong bioaccumulation. Common heavy metal detection includes Inductively Coupled Plasma with Atomic Emission, Spectroscopy (ICP-AES), Inductively coupled plasma mass spectrometry (ICP-MS), Flame Atomic Absorption Spectrophotometry (FAAS), and Graphite Furnace Atomic Absorption Spectrometry (GFAAS), and. However, these technologies are high-cost, time-consuming, complicated operations, and can't be detected immediately and accurately.In this study, we developed an electric double-layer (EDL) extended-gate field effect transistor sensor based on aptamers to detect cadmium ions (Cd2+). Use N-channel enhanced-mode MOSFETs to connect the extended-gate array chips with aptamer modified. The aptamers were self-assembled on the gold electrode surface through Au-S bonds. Since the aptamer has a specific binding ability to cadmium ions, it will bind to the aptamer to form a stem-loop structure. The gate voltage changes caused by the structure change and then amplify the electrical signal through the transconductance of the field effect transistor. The linear detection range of this sensor for cadmium ions is from 1nM to 10uM. The Cd2+ calibration curve is shown a high correlation coefficient (R2 = 0.99001) and an excellent detection limit as low as 99.5 nＭ. Importantly, it responds to Cd2+ within 10 seconds. The sensor exhibits high selectivity in the presence of other heavy metals such as arsenic, chromium, lead, and mercury for electrical signal measurements. It also can be reused without significant signal attenuation.The advantages of this method are convenient portability, short detection time, high sensitivity, and simple operation. It has a good prospect for detection in the daily life of cadmium environmental pollution. Figure 1

Generalizable Electrochemical Biosensors Using DNA-Analyte Conjugates Integrated with Pneumatic Oscillators for Microfluidic Workflow Automation

Sensors based on electrochemical (EC) readout offer low cost, miniaturization, and adaptability to the point-of-care (POC). Nonetheless, most EC sensors are specialized to a particular target, and there remains a need for a robust EC biosensor platform for the multitude of biomarkers that are not EC-active, do not undergo enzymatic conversion, or are not suited for potentiometry [1,2]. While aptamer-based EC sensors have been proven for sensing in living animals with temporal resolution of a few seconds [3], most method development has been target-focused, lacking generalizability [4]. Presently, the clinical EC toolbox is a conglomerate of targeted methods, and there is a pressing need to develop a single EC platform amenable to rapid, generalizable, quantitative readout of multiple classes of clinically relevant targets. A direct, generalized EC sensing approach with minimal added reagents or amplification steps is preferred [5,6]. Our group has been working to address this need and expand to more analyte classes for several years, and in 2019 we designed a versatile DNA-nanostructure architecture attached to gold electrode surfaces [6]. In this work, we will discuss our efforts to expand the generalizability of our sensor platform, chiefly through custom synthesis of varied DNA-analyte bioconjugates to incorporate within the DNA-nanostructure, specifically DNA-peptide and DNA-small molecule conjugates. Using the same DNA nano-architecture, sensors have been validated in 98% human serum for a variety of targets, several encompassing the human clinical range—a peptide drug (exendin-4) [7], a larger protein (creatine kinase), and smaller molecules or steroid hormones (testosterone, estradiol, progesterone, cortisol). Overall, this new DNA nanostructure platform provides a generalizable sensor with minimal workflow, direct-readout, and the capability to expand EC sensing to a wide variety of clinically important analytes. These sensors can measure antibodies directly without any reagent addition, and the small-molecule or peptide sensors require just a two-step workflow. While the workflow is minimal, the EC measurements benefit from well-controlled solution pH, ionic strength, etc. As such, automated fluidic handling can enhance the user-friendliness of the sensors while maintaining measurement quality. We will also discuss several advancements in automating microfluidic flow control, leveraging digital circuit analogies to develop on-chip pneumatic circuits [8,9]. Using devices fabricated by inexpensive, resin-based 3D printers, we have developed robust pneumatic oscillators that can control on-chip valves for pumping solutions to the EC sensors. The oscillators are automated and tunable from 0.5 to 100 Hz and can pump multiple solutions on microdevices with only a single vacuum input line. Antibody reagents and samples can be mixed automatically then introduced to the electrode, and buffer washes can be included to improve measurement consistency. Ultimately, by integrating this automated microfluidic control with our generalizable EC sensors in the future, many different analytes should be measurable consistently and in a user-friendly manner.

A Simple Ratiometric Electrochemical Aptasensor Based on Exonuclease III-Assisted Target Recycling for Ultrasensitive Detection of Prostate Specific Antigen

Prostate specific antigen (PSA) is considered as an important biomarker in prostate cancer diagnosis. Herein, an ultrasensitive ratiometric electrochemical aptasensor was constructed for analyzing PSA. The ferrocene (Fc)-labeled thiolated hairpin probe 2 (Fc-HP2) was conjugated to the gold nanoparticles (AuNPs)-modified gold electrode (AuE) surface by Au-S bonds. With the introduction of PSA, the aptamer region of hairpin probe 1 (HP1) preferred to bind with PSA, and the rest of HP1 could hybridize with Fc-HP2 to form Fc-HP2/HP1/PSA complex with a blunt 3′ terminus, which triggered the exonuclease III (Exo III) cleavage process accompanied by Fc leaving from the electrode and recycling of HP1/PSA. The remaining Fc-HP2 fragments left on the electrode surface were then hybridized with methylene blue-labeled DNA (MB-DNA). This resulted in an enhancement of MB signal (IMB) and a decrement of Fc signal (IFc). Under the optimal conditions, the proposed aptasensor showed good analytical performance for sensitive detection of PSA with a linear range from 100 fg·mL−1 to 10 ng·mL−1 and a detection limit of 34.7 fg·mL−1. The fabricated aptasensor had been applied to detect PSA in diluted human serum samples and obtained satisfied results, suggesting it had great potential in clinical diagnosis.

Electrochemical investigation on naproxen sensing and steady-state diffusion analysis using Ni-Fe layered double hydroxide modified gold electrode

Naproxen, a nonsteroidal anti-inflammatory drug commonly used to treat various types of arthritis, including osteoarthritis, juvenile arthritis, and rheumatoid arthritis, has been associated with serious gastrointestinal and kidney complications. To address this issue, a long-lasting electrochemical sensor capable of sensitively and rapidly detecting naproxen has been developed. The sensor was fabricated by electrodepositing nickel–iron layered double hydroxide (NiFe LDH) on the surface of gold electrode, utilizing ferric nitrate and nickel nitrate as precursors. The NiFe LDH thin film serves as an efficient sensing platform for naproxen determination, and its electrochemical performance was characterized using differential pulse voltammetry and amperometry. Impressively, the developed naproxen sensor boasts a wide dynamic detection range (1–307 μM) and a remarkably low limit of detection of 0.32 μM. Additionally, the NiFe LDH/Au electrode exhibited long-term operational stability of 28 days, rapid response time (<80 s), excellent selectivity, and good reproducibility (1.89% RSD). In addition, Hermite wavelet was employed to formulate the relationship between the steady-state concentration of naproxen and the distance from the electrode's surface. With these impressive attributes, the NiFe LDH modified Au electrode is a promising candidate for the development of a long-lasting and reliable naproxen sensor.

An electrochemical biosensor for detection of T4 polynucleotide kinase activity based on host-guest recognition between phosphate pillar[5]arene and methylene blue

T4 polynucleotide kinase (T4 PNK) is an important DNA repair-related enzyme that plays a crucial role in DNA recombination, replication and damage repair. Herein, an electrochemical biosensor was developed for detection of T4 PNK activity and inhibitor screening based on supramolecular host–guest recognition between phosphate pillar (Dumitrache and McKinnon, 2017) [5] arene (PP5) and methylene blue (MB). The water-soluble PP5 employed as the host for complexation of MB guest molecules. The substrate DNA with 5′-hydroxyl group was first self-assembled on the gold electrode surface through the chemical adsorption of the thiol group, which was phosphorylated in the presence of T4 PNK and adenosine triphosphate (ATP). TiO2 served as a bridge to link phosphorylated DNA and PP5 via the robust phosphate-Ti4+-phosphate chemistry. The immobilized PP5 captured the MB on electrode surface via the supramolecular host–guest recognition interaction, resulting in an enhanced electrochemical response signal. The electrochemical signal is proportional to the T4 PNK concentration in the range of 2 × 10−4 to 5 U mL−1 with a detection limit of 1 × 10−4 U mL−1. It was also successfully used for PNK inhibitor screening and PNK activity assay in HeLa cell lysates sample. The proposed strategy provides a novel sensing platform for kinase activity assay and inhibitor screening, holding a great potential in clinical diagnostics, inhibitor screening, and nucleotide kinase-target drug discovery.

Electrochemical biosensor using SnO2 colloidal quantum wire for monitoring the interaction of microcystin antigen–antibody

Electrochemical sensors that incorporate immunoassay principles have the ability to monitor dynamic processes of antigen–antibody interactions in real time. In this study, a gold electrode was modified with tin dioxide colloidal quantum wire (SnO2 QWs) and then coated with the leucine/arginine subtype microcystin (MC-LR) antibody. The active site of SnO2 QWs that was not bound by MC-LR antibody was then passivated with bovine serum protein (BSA). When the MC-LR antigen binds specifically to the antibodies on the electrode's surface, it triggers electrochemical reactions and generates electrical signals at specific voltage conditions. The SnO2 QW exhibits excellent electron transport ability, and its ability to form a loose and porous microstructure on the gold electrode surface, which is conducive to the receptor function of the biosensor. The results show a high affinity between the MC-LR antigen and antibody, ranging from 1 pg/mL to 10 ng/mL of MC-LR antigen concentration. The kinetic characteristics of the immune reaction between MC-LR antigen and antibody were elucidated, obtaining a binding constant of 1.399 × 1011 M−1 and a dissociation constant of 7.147 pM, demonstrating the potential of electrochemical biosensing technology in biomolecular interactions.

Simple, versatile, and practical impedimetric immunosensor based on gold nanoparticle-polyaniline nanocomposite for clinical dengue virus detection

We constructed a simple, versatile, and practical impedimetric immunosensor for virus detection. The gold nanoparticles (AuNPs) were electrostatically bound to polyaniline (PAni) and subsequently deposited on the surface of the PAni-coated gold electrode. The PAni/AuNPs nanocomposites layer improves the sensor's electroactivity and provides a scaffold to conjugate the antibodies against the targeting virus. The step-by-step fabrication of the immunosensor was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The fabricated sensor was optimized for detecting Norovirus-like particles (NoV-LPs) as a model virus. The sensor displayed a detection limit of 1.80 fg/mL, high specificity, and less than 10% of the coefficient of variation of the detection signal. To prove the sensor's versatility and evaluate its applicability, the anti-Dengue virus (DENV) non-structural protein 1 (NS1) antibody was conjugated into the surface of the electrode. This sensor successfully detected clinical DENV-NS1 samples from patients and discriminated between positive and negative Dengue infection. It indicates the feasibility of the practical immunosensor for virus detection and its potency for large-scale fabrication.